This study will quantitate serum levels of human nerve growth factor and determine its potential role in the etiology of human hypertrophic cardiomyopathy. Previous work from this laboratory has shown that the administration of nerve growth factor (NGF) to newborn puppies results in the development of hypertrophic cardiomyopathy. Hemodynamic and echocardiographic studies, gross pathologic as well as light and electron microscopic findings and determination of myocardial catecholamine content and mitochondrial function suggest some similarities between the NGF-induced cardiomyopathy and human hypertrophic cardiomyopathy. Human nerve growth stimulating activity will be purified from term placenta and its biochemical characteristics compared to those for NGF purified from other species. This material will also be used as a standard for the development of a clinical radioimmunoassay and radioreceptor assay so that NGF levels in patients with hypertrophic cardiomyopathy can be compared with those in matched controls. This study will provide insight into the possible role of abnormalities of the sympathetic nervous system in the genesis of human hypertrophic cardiomyopathy.